PROJECT SUMMARY/ABSTRACT The skeleton is the third most common site of metastatic cancer, and nearly half of all cancers metastasize to bone. As a result of new and aggressive treatments cancer patients are living longer, but at sites of skeletal metastasis fractures occur in 17%-35% of affected bones after minimal trauma. This significantly impacts patient functioning and quality of life. While much has been learned about the mechanisms of skeletal metastasis, clinicians continue to make subjective assessments regarding a patient's fracture risk. We have developed a method, called Computed Tomography-based Rigidity Analysis (CTRA), to use computed tomography (CT) images to calculate the minimal rigidity of a bone containing a neoplastic lesion for the purposes of estimating load capacity and predicting pathologic fractures. The CTRA method has been validated in ex-vivo, pre-clinical, and in-vivo studies. An alpha version of CTRA was developed for research purposes. While it is not intended or marketed for clinical use, it is being used clinically in several different hospitals at the discretion of a medical doctor. Physicians using CTRA have been inconsistently reimbursed by public and private payers under CPT code 76499 ?Unlisted Diagnostic Radiographic Procedure.? This generic code is used when no other specific procedure code exists. At low volumes during initial deployment this is feasible, but for CTRA to become a standard of care, FDA 510(k) clearance and a non-generic Category I CPT code are needed. Through an ongoing Direct Phase II SBIR we are developing a commercial quality CTRA software package that will integrate with hospital picture archiving and communication systems (PACS) and fully automate the CTRA process. This CRP grant will help us bridge the gap between product development and successful medical software commercialization. Therefore, the first two aims fall into the category of Technical Assistance, whereas the last two aims fall into the Late Stage R&D categories follows: Aim 1: prepare all required documentation for an FDA 510(k) submission for CTRA software: Aim 2: prepare an application to the American Medical Association (AMA) for a Category I CPT code: Aim 3: software design verification and validation activities: and Aim 4: eliminate the need for an imaging phantom. Given the clinical need and proven accuracy of the approach, the Musculoskeletal Tumor Society (MSTS) supports the commercialization of CTRA and has already committed to assisting us in the process of applying for a CPT code (see MSTS Letter of Support).